Lightning-arrester.



P. H. THOMAS.

LIGHTNING ARRESTER.

APPLIGATION FILED JUNE 7, 1905.

978,959, Patented Dec. 20, 1910.

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P. H. THOMAS.

LIGHTNING ARRESTER.

APPLIOATION FILED JUNE 7, 1905.

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W/TNESSES /NVENTOR /qvmay M P'. H. THOMAS.

LIGHTNING ARRBSTER.

APPLxoATIoN FILED JUNE 7. 190s.

978,959. Patented Deo. 20, 1910. I

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P. H. THOMAS. LIGHTNING ARRESTER.

- APPLICATION YILBD .TUNE 7,1905. 978,959. Patented De0.20, 1910.

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UNITED STATES PATENT oEETcE.

PERCY H. THOMAS, OF MONTCLIR, NEW JERSEY, ASSIGNOR TO COOPER HEWITTELEC- TRIC COMPANY, OF NEW YORK, N. Y..` A CORPORATION OF NEW YORK.

LIGHTNING-ARRESTER.

Specification of Letten Yatent. Patented Dec, 20, 1910,

Application filed June 7, y1905. Serial No. 264,057.

To all whom 'it may concern:

Be it known that l', Pliner I-l. Thorns, a citizen ofthe linitcd States,and resident of Montclair, county of .llsseyI State of New Jersey, haveinvcnted certain new and useful .Improvements in Lightning- Arresters,'if which the following is a speciiication.

The present invention relates to improvements in lightning arl-esters.

It is well understood that the lightning arrester should be adapted inthe first instance to resist the normal line voltage and to place thellines in connection with the earth upon a rise of potential on the lineto an abnormal or dangerous limit. 'lhiS function is very well performedby an air gap or a number of small air gaps placed between the lille andthe ground. There is, however, another function which should belong to asuccessful lightning arrester and that is the function of interruptingthe current which tends to follow a discharge to ground, such currentbeing supported by the generator itself. Thislast named function is onlyindifferently performed by many types of lightning arrester and thedanger always exists of a leak being established between the line andthe ground by a discharge of abnormally high potential.

It. has been proposed to utilize as a lightning arrester, particularlyin the case of alternating current circuits, a vapor apparatus Such asis typified by the well known mercruy vacuum vapor device. ln utilizingthis device, however, by Simply interposing it between the line and theground, it is found that the device is Somewhat lacking in. adaptabilityby reason of the ditliculty of adjusting reliably to a variety of linevoltages. That is to say, it is nct readily possible to adapt the vapordevice mentioned to the function of permitting an earth discharge on theoccurrence of a predetermined increase of Voltage on the line. On theother hand, the capacity of the mercury vapor device for preventing themaintenance of a current from line to ground through the vapor apparatusbelongs` to the device by virtue of one of its marked characteristics.At the same time the known charzufteristics of the air gap can be quiteSafely relied upon in determining the discharge voltagev of the line.

l propose to make use of the advantages of both the air gap and themercury vapor device b v connecting such devices in series' between theline and the groulid. In connection with Such a. combination, I havefound that there is a considerable number of useful adjuucts whichrender the apparatus more adaptable to commercial circuits as will befully described hereinafter. For example, l may place a resistance orchoke coil, or a condenser or other suitable form of capacity, in shuntto the n'iercury 'apor device. thus throwing practically all thepotential on the spark gap, and l may further use a number of vapordevices in series where the line voltage is so high as to ex# cced thepractical breaking down voltage of a single vapor device. Even in such acase as that last mentioned, it is generallyy desirable to use also aseries spark gap and one or more shunt choke coils, condensers orresistances. An advantage of the use of these Shunting devices is thatthe line voltage is removed from the vapor device or devices at alltimes except during a discharge. And further the. advantage that theshunting devices cause a discharge. voltage to be {irst impressed uponthe air-gap beforeits break down takes place and thereafter upon the'vapor device in virtue of the drop of potential across the shuntdevices, until the former breaks down, when there is a free dischargethroughout the appa atus Furthermore, in case it is diiicult to makeVapor devices sufficiently sensitive and accurate for' a particularcase, it is possible to increase the margin of adaptability of the vapordevice by providing a. choke coil or transformer, or equivalent means,which will cause a sudden rise. of potential upon the vapo-r device atthe time of a discharge from the line. It will thus be seen that. thechief function given to the vapor device 'in the organization describedis that of interrupting the circuit after a discharge. Consequently thisdevice may be used in connection with any lightning arrester either asan adjunct. or for replacing thecurrent rupturing portions of suchlightning arrester.

When a vapor electric apparatus is used `as indi lated herein onlalternating current circuits, it is evident that after a discharge takesplace through the device, current will continue to tiow withoutopposition therefrom, thus vfully discharging the line, until thevoltage is reduced to zero. 'lhereupom since the device is designed toha vc a breaking down point higher than the normal volt` age, unless avoltage greateil than the line voltage of the device is applied, nofurther current iiow through the device will take place in eitherdirection. This follows since the negative electrode resistance. havingonce become established after the discharge, will prevent any furtherflow ot' current un` til broken down by an abnormal voltage, as in thefirst instance. It, however, the line has not by this time beencompletely dis- -charged, the excess voltage will cause a sec` onddischarge through the device and so on until the normal voltage isrestored.

My invention is illustrated in Figures 1, 2, 3, 4, 5, 6, 7 and 8 of thedrawing which are diagrammatic views illustrating different embodimentsof my invention.

In Fig. 1, the line is shown at 1 and a. spark gap having terminals 2and 3 is shown in a circuit, 4, connected to ground at Interposed in thecircuit between the element 3 and the ground is a mercury vapor device,6, having electrodes 7 and 8, which will usually be of mercury, althoughone of the electrodes may be of solid material, such as iron. Across thecircuit between the terminals of the vapor device is arrangedl acircuit, 9, containing a condenser, 10.

The organization shown in Fig. 1 operates as already described in theopening paragraphs of this specification.

In Fig. 2 the condenser 10 is replaced by a resistance 11 and in Fig. 3a reactance device, 12, is substituted for the condenser.

In Figs. 1, 2 and 3, the current translating device in shunt to thevaporvdevice serves to throw the free potential between the line 1 andthe ground 5 upon the air gap 2 3, since the gap 2 3 allowsno leakagecurrent before break down, while the three types of translating devicesof the Figs. 1, 2 and 3 allow an appreciable current flow at allvoltages, thus maintaining the air gap terminal 3 at the potential of 5when no current is passing through the gap 2 3.

In Fig. 4 a reactance device, 13, is placed in series with the vaporapparatus 6, and the condenser 10 is shown across the terminals of the'said apparatus. It will be understood that the condenser may bereplaced by either a resistance or a reactance as lshown in Figs. 2 and3. It is evident that the initial discharge through the air gap 2 3 inthis figure will pass through the current translating device 10 in-shunt, to

. the vapor device 6 and that a certain amount of energy will be storedin the reactance device 13 which will, in general, at least, partiallydischarge itself upon the waning of the first discharge and cause amomentary rise of'potential between the electrodes 7 and 8. lVhen thecurrent translating device is a condenser, this action becomes theabrupt charging of the condenser through a reactance which is well-known to cause a momentary rise of potential in the condenser. Suchrise of potential is obviously of advantage in allowing a more powerfulvapor device 6 andfxzcuring its proper operation.

Fig. 5 shows a series of vapor devices (i, 16, and 26, connected betweenthe sparkga p and ground. Condensers 10, 20 and 30, are s vn'nnetrieallyconnected across the terminals of the respective vapor devices. In placeof the condensers, resistances or reactances may be used as before. Thatis, in Fig. (3, the elements 12, 22, and 32 are reactances, shuntconnected to the vapor device and in Fig. 7, the elements 11', 21, and31 are resistances, similarly connected.

Fig. 5 shows an arrangement similar to Fig. 5, except. thatin additionto the elements of the latter figure, a condenser, 40, is connectedbetween the line terminal of the device 6 and the ground terminal of thedevice 26 and that the air gap 2 3 is made adjustable. In the figure,this is accomplished by mounting the terminal 3 by means of a thread andnut, 50, so that rotation advances or retards this terminal in the usualmanner.

It is, evident in Figs. 5, 5, 6, and 7, that if 'the physicalcharacteristics of the vapor devices, which are connected in series, aremade different that voltage passin the gap 2 3 will be unequallydistribut between these vapor devices so that some one or more will tendto dischar e before the others. After such initial ischarge,"greatlyincreased potential will be im ressed upon the other devices and theyw1ll discharge in their turn. lhns, it is possible to use either agreater number in series when they are so proportioned-as to havesuciently different electrical properties to cause an irregulardistribution of potential between them just'previous to the`discharge ora. iven apparatus caused to discharge at aower volta ge.

The form of circuits which would result from substituting reactances forthe condensers shown in Fig. 5 is illustrated in Fig. 6 and the circuitwhich would result from substituting resistances in a similar manner isillustrated in Fig. 7.

Fig. 8 illustrates a modified form of circuits in which use is made of atransformer having a primary 1 8 in series with the initial dlschargeand a secondary 17 in series with the vapor devices 6, 16 and 26, butnot in serles with the initial discharge connected in such a manner thatthe discharge in passing through 18 tends to cause an increasedpotential upon the vapor devices 6, 16 and .26V above what would be exrienoed were' the transformer not used.4 us it is possible to use vapordevices with a greater margin of safety than would otherwise bepossible. l have shown at 60 and 61 starting hands applied to the vapordevices in proximity to the electrodes and cross connected as shown bylneans of wires 62 and (53. These starting bands may be used inconnection with any of the vapor devices illustrated in the variousfigures of the drawings. In general, such devices are preferablyemployed, although it is not thought necessary to illustrate them inconnect-ion with all the' figures of the drawing. In other cases,however, starting bands are not cross connected but are joined `to thelead wires in immediate proximity thereto. as illustrated, for example,at the right in Fig. S hy the wires G4 and (S5. This prevents aweakening` of the resisting power of the device due to the accidentalelectro-static fields in the neighborhood.

The discharge device illustrated by the elements'Q and 3 in the drawingsmay be made adjustable.

It may be noted in connection with the operation of this device that itsfunction is to discharge freely the high frequency charges ofelectricity which are caused by lightning and which may be due either todirect discharge from the source of light-l ning or to chargeaccun'iulated on account of the electro-static capacity of the wire anddischarge therefrom through the vapor devices while at the same timeserving to interrupt the How of the normal frequency .Current at thenormal voltage of the line.

On account of the well-known nature of lightning, the general system ofapparatus and circuits here described is equivalent to a higlrfrequencydischarge from a high ten sion condenser through an air-gap,representing the original lightning discharge, to-

gether with a secondary discharge of the ner in connection with anyartificially produced initial condenser discharge through aprilnaryair-gap requiring a second discharge gap and arc suppressingdevice, such as is described 1n this invention.

l claim as my invention l. The combination of an electric circuitcarrying alternating current, a suitable ground, an air gap interposedin the ground eircuit,-a vapor device in said circuit, and means forcausing a rise of potential above the discharge line voltage. upon thevapor device as a result of any discharge across the gap.

The combination of an electric circuit carrying alternating current, asuitable ground, an air-gap interposed in the ground circuit, a suitableconnection between said air-gap and the ground, a branch containing avapor device, and a transforming device connected in the said connectionand so related to thel vapor device as to increase the potential appliedto the said vapor device above that applied to the air gap. y

The combination with an electric cir cuit carrying alternating current,a suitable ground, 'an air-gap interposed in the ground circuit, lavapor device in the said circuit, a choke coil in series with thespark-gap and the va )or device, and a capacity so connected lwit thechoke coil that a discharge in the air-gap causes a surge rise ofpotential to be impressed upon the vapor device.

4. rlhe con'ibination of an electric circuit `carrying' alternatingcurrent, a suitable ground, an air-gap interposed in the ground circuit,vapor devices in the said circuit, and means for causing a variationbetween the breaking down points of the several vapor deviceslndividually and collectively.'

5. The combination With an electric circuit carrying, alternatingcurrent, of a suitable ground, an air-ga interposed in the groundcircuit, a plurality of vapor devices in said circuit having differentelectrical characteristics whereby the distribution of potential betweenthem individually and between them and the spark-gap will not Abeuniform.

(l. A vapor device in connection with an air gap as a light-ningarrester, and vaporizable electrodes therefor, and a starting bandco'perating with said electrode, together with means for abruptlyapplying a discharge to the starting band through the air gap.

Signed at v,New York. in the county of New York, and State of New York,this 2nd day of .Tune A. D. 1904.

PERCY H. THOMAS. Witnesses W'M. H. Carni., Tiros. H. BROWN.

